11th ICRS Abstract book - Nova Southeastern University

Oral Mini-Symposium 16: Ecosystem Assessment and Monitoring of Coral Reefs - New Technologies and Approaches
16-26
Solar Irradiance And Coral Reefs: Modeling And Management Tools
Lore AYOUB* 1 , Pamela HALLOCK 1 , Paula COBLE 1
1 College of Marine Science, University of South Florida, St Petersburg, FL
Although mass coral bleachings are generally triggered by supraoptimal seawater
temperatures, experiments have demonstrated that corals and reef-dwelling foraminifers
bleach more readily when exposed to high energy, short wavelength solar radiation (blue,
violet and ultraviolet (UVR; λ ~ 280 - 490 nm). In seawater, colored dissolved organic
matter (CDOM), also called gelbstoff, preferentially absorbs these shorter wavelengths,
which consequently bleach and degrade the CDOM. Alteration and destruction of
watershed and coastal wetlands have reduced natural sources of CDOM that are tidally
flushed into reefal waters. We have measured absorption of UVR and incident UVR at
various reefs in the Florida Keys that differ in distance from shore and the degree of
anthropogenic development and intact mangrove hammock of the adjacent shoreline. The
absorption measurements were used to calculate the intensity of UVR reaching the
benthos. Underwater irradiance (UVR and PAR) was also measured using a multichannel
profiling radiometer. Preliminary results show that reefs associated with intact shorelines
tend to be exposed to lower intensities of UVR than reefs associated with developed
shorelines. Absorption due to CDOM at 320 nm (ag320) also was less variable at reefs
associated with intact shorelines. Inshore reefs tended to be exposed to lower intensities
of UVR than offshore, clear-water reefs at similar depths. Spectral slope of ag for shallow
water coastal areas was modeled from absorption data collected in the spring and summer
of 2004, 2005, 2006 and 2007. Spectral slope was generally greater at offshore sites,
indicating photobleaching of CDOM remaining in offshore waters. These results provide
support for resource managers to protect CDOM sources to reefal waters, such as
preservation of natural coastal vegetation including mangroves and tidal wetlands. Other
potential applications include ground-truthing inherent optical properties and a new
algorithm for satellite-derived measurements of ag and UV Irradiance.
16-27
Light And Motion Sensor Program: Low Cost Coral Reef Monitoring
Burton JONES* 1 , Ivona CETINIC 1 , Gerardo TORO-FARMER 1 , Karli HERZOG 1 ,
Albert BIANCULLI 2 , Ramon DE LEON 3 , Matthew RAGAN 1 , Tom REYNOLDS 1
1 Marine Environmental Biology, University of Southern California, Los Angeles, CA,
2 Sea Monitor Foundation, Bonaire, Netherlands Antilles, 3 Bonaire National Marine Park,
Bonaire, Netherlands Antilles
The “Light and Motion Sensor Program” is an observational network comprised of low
cost sensor arrays deployed along the coral reef on the lee side of Bonaire. This effort is
intended to observe variability of organic components in the water column over the reef
that may indicate nutrient inputs or groundwater seepage into the water column over the
reef. The arrays contain temperature and light sensors at three discrete depths, providing
vertical temperature structure and downwelling light attenuation. Volunteer divers
download the data weekly, transmit it to the laboratory where it is processed and posted
on the web, making the data from the sensor network available in “semi-real time”. Data
collected at each site enable us to follow daily temperature oscillations, and to evaluate
processes that include upwelling, water column mixing, and along-coast propagation of
variability. Downwelling irradiance in three ranges, broadband light, blue and green color
bands, allows the calculation of the diffuse attenuation coefficient for those wave bands.
By coupling measured light with temperature data, it is possible to evaluate the role of
natural and anthropogenic sources affecting fluctuations of light attenuation. The choice
of wavelengths provides an index of the presence of organic matter (Organic Index),
including planktonic algae, dissolved organic matter and detrital material that can affect
the fragile coral reef ecosystem. This unique, inexpensive monitoring network provides
the scientific community and environmental managers with temporal and spatial
information that can be used to assess environmental variability. It can also be used for
recreational purposes by divers and tourists with near real-time observations of the
Bonaire reef environment.
16-28
Novel Optical Technique For Characterization Of Light Absorption And Distribution in
Reef-Building Corals
Vadim BACKMAN* 1 , Erin DALY 2 , Andrew FANG 2 , Margaret SIPLE 2 , Mark WESTNEAT 3 ,
Vladimir TURZHITSKY 1 , Jeremy ROGERS 1 , Luisa MARCELINO 2
1 Biomedical Engineering Department, Northwestern University, Evanston, IL, 2 Civil and
Environmental Engineering, Northwestern University, Evanston, IL, 3 Zoology, Field Museum
of Natural History, Chicago, IL
Light transport in coral skeleton plays an important role in coral physiology. In particular,
characteristic length-scales of light diffusion in coral skeleton (mean free-path length) are long,
which results in the redistribution and homogenization of the illumination of coral tissue and
amplification of light availability to the algal-symbionts by several fold. We describe a novel
optical technique, low-coherence enhanced-backscattering (LEBS), for characterization of light
absorption and distribution in corals. Here we describe the characterization of coral colonies of
different species regarding: 1) the light transport properties of their coral skeleton and tissue; 2)
light absorption by coral tissue; and 3) the micro- and nano-architecture of the coral skeleton
and tissue and their relationship to the optical properties. These findings help to clarify the
efficiency with which different coral species collect and distribute light to their algal-symbionts
and the structure-function relationship in coral skeletons and tissue.
16-29
Patterns Of Vertical Zonation in Mesophotic Reef Communities Of Southwestern Puerto
Rico And Vieques Island
Sara RIVERO* 1 , Roy ARMSTRONG 1
1 Marine Sciences, University of Puerto Rico, Lajas, Puerto Rico
Mesophotic reefs (30-100 m) may be the last frontier in coral reef ecology. These reefs remain
largely unexplored since they require special diving technology or the use of underwater
vehicles for benthic characterizations. Mesophotic reefs in three areas of Puerto Rico: La
Parguera and Guanica, Southwestern Puerto Rico, and Vieques Island were characterized. In
2004 the Seabed Autonomous Underwater Vehicle (AUV) provided seven phototransects of
approximately 1 km which allowed qualitative and quantitative assessments of species
diversity, percent cover, and reef geomorphology. The depths sampled by the AUV ranged from
20-112 m. Percent cover of five main benthic categories were recorded: scleractinian,
macroalgae, gorgonians, sponges, and black corals. Special attention was given to sponges and
scleractinian corals, the latter (mainly Agaricia sp.) were found up to 91 m depth. Coral
dominance (up to 62 % cover) in shallow depths is shifted to sponge dominance (up to 33 %
cover) in deeper areas. Gorgonians, which rapidly disappear after a depth of 40 m are replaced
by black corals. Maximum percent cover for all benthic groups other than scleractinians is at
around 50-60 m depth, which seems to coincide with the lower limit of scleractinian
distribution and increasing availability of bare substrate. The Guanica transects show high
sediment, turbid waters with a higher attenuation coefficient (Kd), lower coral cover and a more
gentle slope than those from La Parguera. Future plans include new deployments of the AUV in
2008 that will permit the assessment of temporal variations within some of these transects, the
role of incident spectral irradiance on community structure, and the assessment of autotrophy
versus heterotrophy in these little-known environments.
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